Vanilla extracts comprising vanillin and other flavor compounds are produced by subjecting ripe green vanilla beans to a curing and extraction process. The curing process forms the brown-black whole vanilla beans available in the super markets. The cured beans can than be extracted to form a liquid vanilla extract.
The enzymatic reactions in the vanilla beans from its precursor glucovanillin to vanillin are believed to be mainly caused by residual plant enzymes, in particular glucosidase enzymes.
The glucovanillin content in perfectly matured vanilla beans is about 10% per weight of dried vanilla beans on average, which can be theoretically converted into a maximum of 4.84% vanillin assuming complete conversion and no losses. Usually, much lower yields are obtained, especially in traditional processes.
Traditional so-called “curing” processes involve scalding, sweating and a long conditioning step that lasts several weeks or months and employs naturally occurring enzymatic reactions.
Prior to sweating and conditioning, the beans usually are subjected to a short (e.g. three minutes) step of scalding in hot water at about 65° C.
During the sweating step, exposure to heat in a humid atmosphere to prevent drying out of beans allows naturally occurring enzymes to convert various precursors including glucovanillin to vanilla flavor components including vanillin.
During the conditioning period which usually lasts many weeks or months, the beans are very slowly dried to allow natural enzymatic reactions to continue. This step involves repeated quality controls and depends on the environmental conditions.
While the sensory profile/flavor of the resulting extracts can be excellent, even under optimal conditions the vanillin yield is very low and usually up to about 2.2% per dry weight of vanilla beans.
Less time consuming processes known in the art either result in a similarly low average vanillin yield, and/or the sensory profile is not acceptable, lacking in complex vanilla aroma and/or containing undesirable off-notes to an extent that almost completely overpowers the vanillin taste even if the yield of vanillin is relatively high, and results in an artificial note not associated with the typical aroma of a vanilla extract formed by traditional several months long curing methods.
For example, some known shorter processes add enzymes to green vanilla beans, for example as described in WO 2004/091316 and U.S. Pat. No. 5,705,205.
WO 2004/091316 describes a combined treatment of extraction and subsequent enzymatic reaction based on green vanilla beans. The enzymatic process employs enzymes with a high lytic activity and a marked cellulase activity (unlike for example beta-glucosidase). These lytic enzymes are used to release the vanillin formed during browning from the plant cells by lysis of the plant cell walls. The accelerated browning step of 0.5 to 7 days is performed by freezing of green vanilla beans followed by thawing, or alternatively, when accepting a lower vanillin yield, by shortly scalding in water at 60° C. to 65° C. and a subsequent sweating step, incubating the scalded beans at 15° C. to 45° C. until brown for a similar time.
U.S. Pat. No. 5,705,205 describes an enzymatic process wherein green freshly harvested beans are hydrated to be ground in water and subjected to various enzymes including, among others, β-glucosidase, the latter to hydrolyze glucovanillin to vanillin.
While improved organoleptically when compared to some earlier enzymatic processes, ripe green (i.e. “uncured”) vanilla beans processed according to known enzymatic processes of short duration (several days up to about a week) still do not develop a comparably complex aroma when compared to traditional curing processes that last for several weeks or months.
Accordingly, there remains a need for a short process that can provide a vanilla bean extract with a good vanillin yield, with an improved sensory profile having a more complex vanilla aroma without off-notes.
In particular, a complex vanilla aroma should comprise a low concentration of desirable phenolic notes (as they will be perceived to be overpowering otherwise), and lack or minimize the very dominant fatty acid off-notes and green off-notes often associated with extracts made from green vanilla beans (rather than cured vanilla beans).
Both traditional curing and the shorter enzymatic processes keep the vanilla beans moist for a significant duration of the process to allow the residual plant enzymes and/or added enzymes to do their work, converting glucovanillin to vanillin.